ok, here's a question that poped up from my head just now.

I've known that ppl are using different sizes of apex seals, like 2mm or 3mm seals, but what's the differences between em? I suppose that 3mm is stronger than 2mm because of the size?

maybe a trivial question for you. I would have done a search if I could.

 

3mm 2-piece seals were stock from '74-85, 3-piece 2mm seals were stock '86-present. (No idea what the RX-8 engine has)

If you're building up an '85-earlier engine, you really don't have a choice but to run 3mm seals. I ain't even touching the 2mm vs. 3mm debate

 

so, let's say I am gonna work on the FD, so I have the choice either go with a 2mm seal or a 3mm seal.

I know 3mm is good, but how different it makes from a 2mm?

 

the apex seals are 80mmL (70 for 12a, 60 for 10a) x about 7.5-90mm tall (this is the wearing demension) and either 2 or 3mm wide. to make things complex mazda didnt only change the width of the seal they changed the design of the 2. the fd comes with the 2mm seals and to put 3mm seals in means you have to machine the rotors from 2mm to 3mm. unfortunatly the size and straightness of the apex seal grooves is very important.

mike

 

I understand that, so does it mean that it's the key idea when you are choosing a rx7 shop? for example, if there are two rx7 shops, one could be quite experienced with machining the grooves for the 3mm seals, and another is so so. Therefore, rebuilt engines from the better shops last longer? I guess there also has to be a lil bit engine tunning involved?

 

theres a company in canada that makes
2mm, 3mm, 3.5mm, 4mm and 6mm Apex Seals
http://www.rotaryengine.ca/

 

yeah, but I mean I wanna know some general knowledge about the size of apex seal, I think I've found out the answer.

 

it really matters how you machine the apex seal grooves

mike

 

6mm?! That's unheard of! can use 3 of those babies in one slot?

 

3mm stronger but heavier,2mm ligther but not as strong, 3mm takes more detonation then a 2mm, 3mm don't seal as good as the 2mm, 3mm have a tendency to warpppp like a banana 2mm don't. U could go back and forth it's a give and take. Remember the research and development department @ Mazda is always looking for what is better as far as Apex seals. When they changed to the 2mm 3 piece apex seal dual spring in 1986 was for a good reason. A very good "tuned" 13B 2mm apex seal engine will last a life timeeeeeeeee...

 

6 mm ?? LOL those can be used as counter weights

 

Not when they're made out of carbon................

 

WOW ancient thread

The apex seals do not factor into the balance of the rotating assembly. Their weight is supported by the rotor housing, not the eccentric shaft.